Utilizing Angular 2's ngModel feature for dynamic objects and properties

Question

Utilizing Angular 2's ngModel feature for dynamic objects and properties

Within my TypeScript file, I am dynamically generating properties on the object named selectedValsObj in the following manner:

private selectValsObj: any = {};

setSelectedValsObj(sectionsArr) {
  sectionsArr.forEach(section => {
    section.questions.forEach(questionObj => {
      if (questionObj.type === 'drop-down') {
        this.selectValsObj[questionObj.questionId] = { selected: questionObj.answerDetails[0] };
      }
    })
  });
}

When it comes to the HTML part, I desire to bind the [ngModel] attribute of my inputs to the properties existing within the selectValsObj object. Despite attempting various approaches, I have not been able to achieve the desired outcome:

<div *ngFor="let question of section.questions">
    <div class="drop-down-question" *ngIf="question?.type === 'drop-down'">
        <select class="q-select"
                [(ngModel)]="selectValsObj[questionId].selected" // <== doesn't work either**
                // [(ngModel)]="selectValsObj[{{ questionId }}].selected" // <== also doesn't work**
                name="answerForQuestion{{ question?.questionId }}">
            <option *ngFor="let answer of question?.answerDetails"
                [ngValue]="answer">
                    {{ answer?.value }}
            </option>
        </select>
    </div>
</div>

Is there a way for me to properly assign the ngModel within my HTML to a property that is created dynamically within my TypeScript file?

angular typescript angular2-ngmodel

Answer 1

Answer №1

Upon attempting to replicate the scenario, I noticed multiple issues within the code snippet you provided.

The property selectValsObj is declared as private, yet it is being utilized in the template.
In the template, there is an attempt to iterate over section.questions, but this array is not defined elsewhere apart from the setSelectedValsObj method's local scope.
You may be misusing your data due to a lack of type definitions.

This revised version includes inferred type definitions:

interface QuestionModel {
  type: string;
  questionId: string;
  answerDetails: string[];
}

const MOCK_DATA = [
  {
    questions: [{
      type: 'drop-down',
      questionId: '42',
      answerDetails: ['wololo'],
    }],
  },
];


@Component(...)
export class ProductsComponent {
  selectValsObj: { [key: string]: { selected: string } } = {};

  constructor() {
    this.setSelectedValsObj(MOCK_DATA);
  }

  setSelectedValsObj(sectionsArr: { questions: QuestionModel[] }[]) {
    sectionsArr.forEach(section => {
      section.questions.forEach(questionObj => {
        if (questionObj.type === 'drop-down') {
          this.selectValsObj[questionObj.questionId] = {selected: questionObj.answerDetails[0]};
        }
      });
    });
  }
}

Prior to implementation, ensure the type definitions align with your intentions to reduce potential errors.

Additionally, consider adopting a more declarative approach by utilizing map and filter for data manipulation instead of relying solely on forEach.

Answer 2

Upon attempting to replicate the scenario, I noticed multiple issues within the code snippet you provided.

The property selectValsObj is declared as private, yet it is being utilized in the template.
In the template, there is an attempt to iterate over section.questions, but this array is not defined elsewhere apart from the setSelectedValsObj method's local scope.
You may be misusing your data due to a lack of type definitions.

This revised version includes inferred type definitions:

interface QuestionModel {
  type: string;
  questionId: string;
  answerDetails: string[];
}

const MOCK_DATA = [
  {
    questions: [{
      type: 'drop-down',
      questionId: '42',
      answerDetails: ['wololo'],
    }],
  },
];


@Component(...)
export class ProductsComponent {
  selectValsObj: { [key: string]: { selected: string } } = {};

  constructor() {
    this.setSelectedValsObj(MOCK_DATA);
  }

  setSelectedValsObj(sectionsArr: { questions: QuestionModel[] }[]) {
    sectionsArr.forEach(section => {
      section.questions.forEach(questionObj => {
        if (questionObj.type === 'drop-down') {
          this.selectValsObj[questionObj.questionId] = {selected: questionObj.answerDetails[0]};
        }
      });
    });
  }
}

Prior to implementation, ensure the type definitions align with your intentions to reduce potential errors.

Additionally, consider adopting a more declarative approach by utilizing map and filter for data manipulation instead of relying solely on forEach.

Answer 3

Answer №2

Review the HTML code snippet below:

[(ngModel)]="selectValsObj[questionId].selected"

If you have not defined a variable named questionId with a value in your TypeScript file, this could be causing an issue.

To obtain the questionId for each question within your section.questions loop, consider using the following modification:

[(ngModel)]="selectValsObj[question.questionId].selected"

I've included a simple example demonstrating various scenarios in this link (located in the src/app.ts). Hopefully, it provides some assistance.

Answer 4

Review the HTML code snippet below:

[(ngModel)]="selectValsObj[questionId].selected"

If you have not defined a variable named questionId with a value in your TypeScript file, this could be causing an issue.

To obtain the questionId for each question within your section.questions loop, consider using the following modification:

[(ngModel)]="selectValsObj[question.questionId].selected"

I've included a simple example demonstrating various scenarios in this link (located in the src/app.ts). Hopefully, it provides some assistance.

Answer 5

Answer №3

(click)="toggle(personnel.id)"
  *ngIf="isToggled[personnel.id]"

in typescript file:

isToggled: any = {};

inside toggle method,

this.isToggled[personnelId] = !this.isToggled[personnelId];

Answer 6

(click)="toggle(personnel.id)"
  *ngIf="isToggled[personnel.id]"

in typescript file:

isToggled: any = {};

inside toggle method,

this.isToggled[personnelId] = !this.isToggled[personnelId];

Answer 7

Answer №4

Your intentions seem a bit unclear at the moment.
It appears that you are aiming to dynamically construct a page featuring questions and answers in a drop-down format, along with capturing the selected answer.
If this is the case, the code snippet below may be of assistance.

If so, the following Angular code can guide you:

import { Component, OnInit } from '@angular/core';

interface Question {
  questionStr: string;
  questionId: string;
  type: string;
  answers: Array<string>;
  selectedAnswer: string;
}

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
  title = 'app';

  selectValsArr: Array<Question> = [];

  ngOnInit() {
    this.setSelectedValsObj([
      {
         questionStr : 'Question1',
         questionId: 'Q01',
         type: 'drop-down',
         answers: ['Q1Ans1', 'Q1Ans2', 'Q1Ans3'],
         selectedAnswer: null
      },
      {
        questionStr: 'Question2',
        questionId: 'Q02',
        type: 'drop-down',
        answers: ['Q2Ans1', 'Q2Ans2', 'Q2Ans3'],
        selectedAnswer: null
      },
    ]);
  }


  setSelectedValsObj(sectionsArr: Array<Question>) {
    sectionsArr.forEach(section => {
      if (section.type === 'drop-down') {
        this.selectValsArr.push(section);
        }
    });
  }
}

and HTML

<div *ngFor="let question of selectValsArr">
  <h3>{{question.questionStr}}</h3>
  <div class="drop-down-question">
    <select [(ngModel)]="question.selectedAnswer">
      <option value="">Select an Answer</option>
      <option *ngFor="let ans of question.answers" [ngValue]="ans"> {{ans}}</option>
    </select>
  </div>
</div>

<br>
<h2>Selected Answer</h2>

<div *ngFor="let question of selectValsArr">
    <span>{{question.questionStr}}</span>
    <span>&nbsp; &nbsp; - &nbsp; {{question.selectedAnswer}}</span>
</div>

Answer 8

Your intentions seem a bit unclear at the moment.
It appears that you are aiming to dynamically construct a page featuring questions and answers in a drop-down format, along with capturing the selected answer.
If this is the case, the code snippet below may be of assistance.

If so, the following Angular code can guide you:

import { Component, OnInit } from '@angular/core';

interface Question {
  questionStr: string;
  questionId: string;
  type: string;
  answers: Array<string>;
  selectedAnswer: string;
}

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
  title = 'app';

  selectValsArr: Array<Question> = [];

  ngOnInit() {
    this.setSelectedValsObj([
      {
         questionStr : 'Question1',
         questionId: 'Q01',
         type: 'drop-down',
         answers: ['Q1Ans1', 'Q1Ans2', 'Q1Ans3'],
         selectedAnswer: null
      },
      {
        questionStr: 'Question2',
        questionId: 'Q02',
        type: 'drop-down',
        answers: ['Q2Ans1', 'Q2Ans2', 'Q2Ans3'],
        selectedAnswer: null
      },
    ]);
  }


  setSelectedValsObj(sectionsArr: Array<Question>) {
    sectionsArr.forEach(section => {
      if (section.type === 'drop-down') {
        this.selectValsArr.push(section);
        }
    });
  }
}

and HTML

<div *ngFor="let question of selectValsArr">
  <h3>{{question.questionStr}}</h3>
  <div class="drop-down-question">
    <select [(ngModel)]="question.selectedAnswer">
      <option value="">Select an Answer</option>
      <option *ngFor="let ans of question.answers" [ngValue]="ans"> {{ans}}</option>
    </select>
  </div>
</div>

<br>
<h2>Selected Answer</h2>

<div *ngFor="let question of selectValsArr">
    <span>{{question.questionStr}}</span>
    <span>&nbsp; &nbsp; - &nbsp; {{question.selectedAnswer}}</span>
</div>

Utilizing Angular 2's ngModel feature for dynamic objects and properties

Answer №1

Answer №2

Answer №3

Answer №4

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